The present invention relates to a suppression circuit, in particular for suppressing the noise of the wiper motor of a motor vehicle, the suppression circuit being provided with at least two capacitors, which are situated between one common terminal and two separate terminals, it also being provided with pulse limitation, of the species defined in the preamble of claim 1.
From the German Design Patent 2 96 19 780.7, a suppression device is known for suppressing the noise of the wiper motor of a motor vehicle. In this context, the suppression circuit contains two capacitors, which are situated between one common and two separated terminals. Furthermore, to improve the suppression, pulse limitation is provided, which is realized by a varistor parallel to each capacitor.
A varistor is a relatively expensive component requiring considerable space. It is known that the limiting function of the varistor, with respect to the positive and negative voltage pulses, can also be realized by an anti-serial circuit arrangement having two Zener diodes. Components of this type combined in one enclosure are known and are available as bidirectional Zener diodes. However, as a result of the comparatively low quantities in comparison with standard, conventional components, such as diodes and Zener diodes, their price is disproportionately high.
In contrast, the suppression circuit according to the present invention, in particular for suppressing the noise of the wiper motor of a motor vehicle, having the characterizing features of claim 1, has the advantage of making available a simple and reliable solution in which the costs are reduced and lower space requirements are achieved. The number of soldering or welding points, of points of connection generally, is small, so that in addition to the advantage of using cost-effective components such as Zener diodes and diodes, the advantage of a simpler production process is also achieved. As a result of the fact that the number of points of connection is reduced, the sources of errors arising in soldering or welding are also significantly reduced.
In the suppression circuit according to the present invention, for the general purpose of pulse limitation, the series circuit composed of the cathode-anode path of a diode and the anode-cathode path of a Zener diode is connected in parallel to each capacitor. In this context, for use in a motor, the component facing the negative terminal clamp is the Zener diode having its cathode. With respect to the positive terminal clamp, the blocking effect of a simple diode is exploited, the cathode of the diode being connected to the terminal.
As result of the measures laid down in the further claims, advantageous refinements and improvements of the suppression circuit indicated in claim 1 are possible.
According to one particularly expedient refinement of the present invention, it is provided that the anodes of the diodes and of the Zener diode are connected together at one point.
In one preferred, advantageous embodiment of the suppression circuit according to the present invention, in using two capacitors, a single Zener diode is provided for both parallel circuits. In this manner, a version is created that is very simple and, in practice, very cost-effective and space-saving.
In one particularly advantageous and expedient refinement of the present invention, it is embedded, as a suppression module, in a suppression device, which is provided in a capacitor enclosure. In accordance with one advantageous embodiment of this refinement of the present invention, the capacitor enclosure has three contact terminals, which stand in a fixed spatial relationship to each other, irrespective of the number of suppression components. In a further embodiment, the capacitor enclosure has a block-like or cuboid shape.